This invention relates generally to computing systems and more particularly to restricting copying of video signals.
Unauthorized copying of copyrighted work is, unfortunately, very prevalent. Such unauthorized copying ranges from simple copying of a few pages of a copyrighted book to widespread distribution of millions of dollars worth of illegally copied movies, compact discs, and other entertainment medium.
With the advent of digital videodiscs (DVD), the illegal copying of DVDs is of great concern to content companies (i.e., the companies owning the copyrighted work recorded on the DVDs). To protect the copyrighted works, content companies are demanding that DVD producers incorporate a security mechanism to prevent unauthorized copying. One such recommended security mechanism is currently being used in conjunction with videocassette recorders and was developed by Macrovision. The Macrovision technique (hereinafter referred to as Macrovision) essentially places additional coding in the vertical blanking interval and/or horizontal sync signals of a video stream provided to a television for display. The television filters out the additional coding with negligible adverse video effects, but a videocassette recorder (VCR) is not able to filter out the additional coding, thereby preventing the VCR from making quality copies.
While Macrovision prevents VCRs coupled to televisions from making quality copies, it does not prevent unauthorized copying by a personal computer (PC) that is coupled to a VCR and/or any other video source (including a DVD player, television broadcast, cable broadcast, etc). As is generally know, a PC may be equipped with an analog video decoder, such as the one contained in the All-in-Wonder Board manufactured and distributed by ATI International, which converts an analog video signal into a digital video data stream. The analog-to-digital conversion (ADC) of the analog video stream removes the Macrovision encoding. As such, the PC may copy the digital video data stream without degradation since the Macrovision encoding has been removed. Such potential unauthorized copying is unacceptable to content providers.
Therefore, a need exists for a method and apparatus that restricts a video output based on copy protection information, such as Macrovision.